Communication Libraries¶

This section covers MAVLink communication, RC protocols, telemetry, and serial interfaces.

MAVLink Protocol ¶

GCS_MAVLink (Ground Control Station Communication)¶

Header: libraries/GCS_MAVLink/GCS_MAVLink.h

Description: MAVLink protocol implementation for communication with ground stations (QGroundControl, Mission Planner, etc.).

class GCS_MAVLINK¶

MAVLink transport control class.

Subclassed by GCS_MAVLINK_Dummy

Public Functions

void void queued_param_send (): Send the next pending parameter, called from deferred message handling code.

inline uint16_t txspace() const¶: Check for available transmit space.

Protected Functions

void handle_serial_control(const mavlink_message_t &msg)¶: handle a SERIAL_CONTROL message

Protected Attributes

AP_Param *_queued_parameter¶: next parameter to

Private Members

AP_HAL::UARTDriver *_port¶: The stream we are communicating over.

enum ap_var_type _queued_parameter_type¶

type of the next

Perform queued sending operations

uint16_t _queued_parameter_index¶

AP_Param token for.

next queued

uint16_t _queued_parameter_count¶: saved count of

struct deferred_message_bucket_t¶

struct deferred_message_t¶

struct LastRadioStatus¶

struct pending_param_reply¶

struct pending_param_request¶

struct stream_entries¶

Usage Example:

// Send message to ground station
gcs().send_text(MAV_SEVERITY_INFO, "Hello World");
gcs().send_location(location);
gcs().send_heartbeat();

Common Messages:

send_text() - Send text message
send_location() - Send GPS location
send_heartbeat() - Send heartbeat
send_statustext() - Send status text

Related Types:

mavlink_message_t
MAV_SEVERITY
MAV_CMD_*

GCS (GCS Base Class)¶

Header: libraries/GCS_MAVLink/GCS.h

Base GCS class for common GCS functionality.

class GCS¶

global GCS object

Subclassed by GCS_Dummy

struct statustext_t¶

class StatusTextQueue : public ObjectArray<statustext_t>¶

RC Input Protocols ¶

AP_RCProtocol (RC Input)¶

Header: libraries/AP_RCProtocol/AP_RCProtocol.h

Description: RC (Radio Control) input protocol handler supporting multiple receiver types.

Supported Protocols:

PPM - Pulse Position Modulation
SBUS - Futaba SBUS
CRSF - Crossfire (ELRS)
DSM - DSM/DSMX (Spektrum)
SRXL - SRXL
ST24 - Spektrum ST24
SBus - SBus (inverted)

Usage Example:

#include <AP_RCProtocol.h>

AP_RCProtocol *rc_protocol = AP_RCProtocol::get_singleton();

// Get detected protocol
AP_RCProtocol::rcprotocol_t proto = rc_protocol->protocol_detected();
const char *name = rc_protocol->protocol_name_from_protocol(proto);

RC_Channel (RC Input Channel)¶

Header: libraries/RC_Channel/RC_Channel.h

Description: RC channel handling for pilot input.

Detailed Documentation:

RC_Channel Detailed Reference - Detailed RC_Channel API Reference

Usage Example:

RC_Channel *rc = RC_Channel::rc_channel(0);  // Channel 1

// Get input
float input = rc->norm_input();  // -1 to 1 or 0 to 1
int16_t pwm = rc->get_radio_in();  // 1000-2000

SRV_Channel (Servo Output)¶

Header: libraries/SRV_Channel/SRV_Channel.h

Description: Servo output channel handling.

Usage Example:

SRV_Channel *servo = SRV_Channel::srv_channel(0);  // Servo 1

// Set output
servo->set_output_pwm(1500);  // Set PWM

Serial Communication ¶

AP_SerialManager (Serial Port Manager)¶

Header: libraries/AP_SerialManager/AP_SerialManager.h

Description: Manages serial ports for GPS, telemetry, MAVLink, etc.

Usage Example:

AP_SerialManager *serial = AP_SerialManager::get_singleton();

// Get serial by protocol
AP_HAL::UARTDriver *uart = serial->get_serial(AP_SerialManager::SerialProtocol_MAVLink);

Telemetry ¶

AP_RCTelemetry (RC Telemetry)¶

Header: libraries/AP_RCTelemetry/AP_RCTelemetry.h

Description: RC telemetry for reporting RSSI, link quality, etc.

MAVLink Routing ¶

MAVLink messages can be routed between different interfaces:

Serial ports
UDP/TCP
CAN bus (DroneCAN)
RSSI reporting

Common MAVLink Messages: